Food Chemistry 121 (2010) 406–411

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Food Chemistry

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Influence of conventional and organic agricultural practices on the phenoliccontent in eggplant pulp: Plant-to-plant variation

Devanand Luthria a,*,1, Ajay P. Singh b,1, Ted Wilson c, Nicholi Vorsa d, Gary S. Banuelos d, Bryan T. Vinyard e

a Food Composition and Methods Development Lab, BHNRC, 10300 Baltimore Ave., Bldg 161 BARC-East, Beltsville, MD 20705-2350, United Statesb Rutgers, The State University of New Jersey, Department of Plant Biology and Pathology, 59 Dudley Road, New Brunswick, NJ 08901, United Statesc Department of Biology, Winona State University, Winona, MN 55987, United Statesd Water Management Research Laboratory, Agricultural Research Service, US Department of Agriculture, Parlier, CA 93648, United Statese Biometrical Consulting Service, Beltsville Agricultural Research Center, US Department of Agriculture, Beltsville, MD 20705, United States

a r t i c l e i n f o a b s t r a c t

Article history:Received 28 September 2009Received in revised form 7 December 2009Accepted 15 December 2009

Keywords:Eggplant (Solanum melongena L.)PolyphenolsConventional and organic5-Caffeoylqunic acidHPLC and LC–MS analysisTotal phenolicsFolin–CiocalteuPlant-to-plant variations

0308-8146/$ - see front matter Published by Elsevierdoi:10.1016/j.foodchem.2009.12.055

* Corresponding author. Tel.: +1 301 504 7247; faxE-mail address: D.Luthria@ars.usda.gov (D. Luthria

1 Both authors have equal contribution.

Consumer awareness, pesticide and fertiliser contaminations, and environmental concerns have resultedin significant demand for organically grown farm products. The present study evaluates the influence thatorganic and conventional farming practices exert on the total phenolic content in eggplant samples fromtwo cultivars, Blackbell (American eggplant) and Millionaire (Japanese eggplant), grown by conventionaland organic farming practices with similar climatic conditions. In addition, plant-to-plant variation inphenolic content was determined from eight eggplant samples collected from different plants grownat various field positions. Samples were separately assayed for phenolic content by the two independentprocedures, HPLC/LC–MS and Folin–Ciocalteu assay. The results of the HPLC analysis showed significantplant-to-plant variation (% RSD ranged from 22% to 48%) in 5-caffeoylqunic acid content (the most abun-dant phenolic acid) in eight eggplant samples collected from eight different plants belonging to the samecultivar and grown under similar conditions. The cv. Millionaire showed a higher total phenolic contentcompared to the Blackbell cultivar. We did not observe significant consistent trend in the phenolic con-tent of eggplant samples grown with organic and conventional farming practices with both eggplant cul-tivars. We, however, observed a strong correlation (R2 = 0.87) between total phenolic content as assayedby Folin–Ciocalteu assay and 5-caffeoylqunic acid, a major phenolic acid in eggplant extract. This studyconcludes that multiple repetitive analyses of plant products collected from different plants grown overvarious time periods (seasons) at different locations should always be carried to unambiguously provethe impact of growing conditions on phenolic content or antioxidant activity.

Published by Elsevier Ltd.

1. Introduction

Consumption of the phytochemicals in fruits and vegetables,particularly phenolic compounds, has been linked to reduced riskof coronary heart diseases, neurodegenerative diseases, and certainforms of cancers (Halliwell, 1994; Huang & Ferraro, 1992; Hunget al., 2004). The research on antioxidant activity of eggplant withdifferent assays was published by Huang et al. (2004). Eggplant(Solanum melongena L.), is ranked among the top ten vegetablesin terms of oxygen radical absorbance capacity due to the fruitphenolic constituents (Cao, Sofic, & Prior, 1996). Eggplant fruit isalso commonly known as aubergine, melanzana, garden egg, brin-jal, or patlican in different parts of the world. The colour, size, andshape of the eggplant fruit varies significantly with the type of the

Ltd.

: +1 301 504 8314.).

eggplant cultivar. Sudheesh, Presannakumar, Vijayakumar, and Vi-jayalakshmi (1997) showed the hypolipidemic beneficial effect ofphenolic phytochemicals from S. melongena in normal and choles-terol fed animals.

It is well documented in several peer-reviewed publicationsthat the quantity and quality of phenolics present in fruits and veg-etables are significantly influenced by cultivar, environment, soiltype, growing, and storage conditions (Achouri, Boye, & Belanger,2005; Antolovich, Prenzler, Robards, & Ryan, 2000; Grifith, & Colli-son, 2001; Lee, Renita, Fioritto, Martin, Schwartz, & Vodovotz,2004; Luthria, 2006; Naczk, & Shahidi, 2004; Robbins, 2003). Thecomposition of phenolic phytochemicals in fruits and vegetablesmay also be influenced by the mode of farming, i.e. conventionalvs. organic. Proponents of organic farming often claim that organ-ically derived fruits, vegetables, and grains are more beneficial forhuman health as they are grown without the aid of synthetic pes-ticides. In some publications, it is stated that organically growncrops contain higher antioxidant content (Chassy, Bui, Renaud,

D. Luthria et al. / Food Chemistry 121 (2010) 406–411 407

Horn, & Mitchell, 2006; M del Amor, Serrano-Martinez, Fortea, &Nunez-Delicado, 2008; Woese, Lange, Christian, & Bogl, 1997)while others show inconsistent differences in the antioxidant con-tents (Dimbergh, Gissen, & Nilsson, 2005; Lombardi-Boccia, Luca-rini, Lanzi, Aguzzi, & Cappelloni, 2004). A recently publishedscientific status summary by the Institute of Food Technologists(Winter & Davis, 2006) concluded that it is premature to say thateither organic or conventional foods are better in terms of safetyor nutritional values. However, the global market for certified or-ganic foods is rapidly growing in both the United States and Europe(Kortbech-Olesen, 2003). This increased demand for certified or-ganic foods has necessitated a need for quantification of pesticides,nutrients, and other bioactive phenolics in foods grown under bothconventional and organic environments.

In an earlier publication, we initially developed an optimizedmethod for the extraction of phenolic acids from eggplant fruit(Luthria & Mukhopadhyay, 2006) and later described extractionand analysis of polyphenols from eggplant pulp along with theinhibition of cupric-ion mediated oxidation of low-density lipopro-tein (Singh et al., 2009). A large number of the earlier publishedstudies on phenolics and their antioxidant activity of eggplantsor other fruits and vegetable extracts were usually carried out withlimited number of samples per cultivar or growing conditions. Incontinuation of our research on eggplant phenolics, we systemati-cally examined the phenolics content of 32 eggplant samples. Eightsamples per cultivar (Blackbell-American and Millionaire-Japa-nese) per growing conditions (organic and conventional) were col-lected from eight separate plants grown in different locations ofthe same field. This study was undertaken to evaluate plant-to-plant variation of phenolic content in eggplants samples collectedfrom different plants. In addition, influence of organic and conven-tional farming on eggplant phenolics and their antioxidant activitywas also evaluated. The phenolic content in eggplant samples wasdetermined by two independent procedures, high performance li-quid chromatography with diode array detection and a spectro-photometric Folin–Ciocalteu (FC) assay.

2. Materials and methods

2.1. Plant materials

Two of the most popular hybrid cultivars of eggplants (S. melon-gena L.) developed in the United States (cv. Blackbell) and in Japan(cv. Millionaire) were used for the study. Both varieties weregrown in a Hanford sandy loam soil under both conventional grow-ing conditions at Israel Alvarez Farm and under organic conditionsat T and D Willey Farms near Fresno, CA (USA). Eggplant fruitswere randomly harvested in June 2005 from different plants fromvarious locations at each field site and sent overnight to the FoodComposition and Methods Development Laboratory, Beltsville,MD (USA).

2.2. Chemicals

Folin–Ciocalteu (FC) reagent, gallic acid, and sodium carbonatefor the assay of total phenolics (TP) were obtained from SigmaChemicals (St. Louis, MO, USA). 5-Caffeoylquinic acid standardwas purchased from Indofine Chemicals (Hillsborough, NJ, USA).HPLC grade methanol and acetonitrile, formic acid, and water wereobtained from Fisher Scientific (Fair Lawn, NJ, USA). Polyvinylidenedifluoride (PVDF) syringe filters with pore size 0.45 lm were pur-chased from National Scientific Company (Duluth, GA, USA). Deion-ized water (18 MX) was prepared using a Millipore Milli-Qpurification system (Millipore Corp., New Bedford, MA, USA).

2.3. Sample preparation

As described earlier (Luthria & Mukhopadhyay, 2006; Singh et al.,2009) all eggplant samples were peeled, and the pulp and the flesh ofthe fruits were separated. The flesh of the fruits was chopped intosmall pieces (2–4 cm) and stored in Ziploc bags under nitrogen attemperature <�60 �C. The frozen flesh part of the fruits was lyophi-lized and the freeze-dried sample was ground in a coffee grinder. Thedried ground powder was passed through a standard 20 mesh size(particle size < 0.850 mm). The homogenized freeze-dried groundmaterial was well mixed and stored in 2–5 g aliquots under nitrogenat temperature <�60 �C until extracted and analyzed.

2.4. Sample extraction

Extraction was carried out using an optimized procedure usinga pressurized liquid extractor (Luthria & Mukhopadhyay, 2006). Inshort, an accelerated solvent extractor (ASE) from Dionex Corpora-tion (Model ASE 200, Dionex Corporation, Sunnyvale, CA) was usedfor PLE. Aliquots of 250 ± 1 mg of dried powdered eggplant sampleswere placed in an 11 mL stainless steel extraction cell. Two circularcellulose filters (size 1.983 mm, Dionex Corporation) were placedat the bottom of the extraction cell in order to prevent suspendedparticles from entering the collection vials. The remaining void vol-ume in the cell was filled with Ottawa Sand. Both extraction cellsand collection vials were arranged appropriately in the two desig-nated carousels. Extractions were carried out with an optimizedsolvent mixture (MeOH/H2O, 80:20, % v/v). Extractions were per-formed at 1000 psi, 100 �C, with a 5 min equilibration time, a5 min static time, and a 90 s purge time for each extraction cycle.A total of four extraction cycles were performed for each sample.About 20 mL of solvent was used for the four extraction cycles withflush volume set at 75%. Extracts were collected in a 60 mL ambersample vials fitted with Teflon coated rubber caps (I-CHEM, NewCastle, DE, USA). Each extract was transferred to a 25 mL volumet-ric flask and the total volume was adjusted to 25 mL with appropri-ate solvent mixture. Aliquots of eggplant extracts were filteredthrough a 0.45 lm PVDF syringe filter prior to analysis of phenolicacids by HPLC with diode array detection. Triplicate extractionsand HPLC analysis were carried out for each sample.

2.5. Determination of phenolics by FC assay

The phenolic content was determined with the FC assay proce-dure using gallic acid as a standard on a Perkin–Elmer Lambda 25spectrophotometer (Waltham, MA, USA) as described in our earliercommunication (Mukhopadhyay, Luthria, & Robbins, 2006). Theabsorbance of the colored reaction product was measured at765 nm. Calibration curve was produced using standard gallic acidsolutions each time analysis was run and the level of TP in the extractwas determined. The phenolic content in the extract was calculatedfrom the standard calibration curve. Results were expressed in mg ofgallic acid equivalents per gram (GAE/g) of dried eggplant pulp.

2.6. HPLC and LC–MS analysis

Phenolic compounds were identified by high performance li-quid chromatography coupled with tendem mass spectrometry(HPLC/MS/MS) as described in our earlier communication (Singhet al., 2009). An HPLC/UV method developed in our laboratorywas used for the detection and quantification of phenolic acid(Luthria & Mukhopadhyay, 2006; Robbins, 2003). Eggplant extractswere analyzed on a Beckman Coulter HPLC System Gold coupled toa programmable detector (System Gold, series 166) and an auto-sampler (System Gold, series 508) operated by a 32 Karat softwarepackage (Beckman Coulter, Fullerton, CA, USA). A reversed phase

Fig. 1. A typical HPLC profile of phenolic phytochemical extracted from eggplant pulp sample extracted with 80% aqueous methanol. The major compound was identified as5-caffeoylqunic acid (peak 3).

408 D. Luthria et al. / Food Chemistry 121 (2010) 406–411

C18 Luna column (Phenomenex, Torrance, CA, USA, 150 � 4.6 mm;particle size 5 lm), preceded by a guard column (Phenomenex,4 � 3.0 mm) of the same stationary phase was used for HPLC anal-ysis. The column and the guard column were thermostatically con-trolled at 25 �C and the flow rate was set to 0.7 mL/min. The mobilephase consisted of two solvents; 0.1% formic acid (A) and MeOH

Table 1HPLC analysis results of 5-caffeoylquinic acid extracted from 32 eggplants belonging toconditions (organic and conventional). Triplicate extraction and HPLC analysis was carried

Cultivars Growing conditions 5-CaffeoylquinicAcid mean(mg/g) DMB(n = 3)

Blackbell Conventional 2.24Blackbell Conventional 3.14Blackbell Conventional 3.67Blackbell Conventional 8.3Blackbell Conventional 2.64Blackbell Conventional 5.51Blackbell Conventional 3.14Blackbell Conventional 4.21

Blackbell Organic 1.57Blackbell Organic 1.36Blackbell Organic 2.59Blackbell Organic 4.04Blackbell Organic 3.58Blackbell Organic 1.66Blackbell Organic 3.72Blackbell Organic 2.52

Millionaire Conventional 7.92Millionaire Conventional 8.02Millionaire Conventional 5.73Millionaire Conventional 5.17Millionaire Conventional 4.95Millionaire Conventional 4.73Millionaire Conventional 6.3Millionaire Conventional 4.72

Millionaire Organic 5.7Millionaire Organic 10.35Millionaire Organic 7.59Millionaire Organic 7.81Millionaire Organic 5.99Millionaire Organic 4.76Millionaire Organic 5.2Millionaire Organic 6.27

(B). The mobile phase gradient in volumetric ratio of solventswas as follows: 5–30% B over 50 min. The solvent gradient washeld at 30% B for additional 15 min and at 65 min gradient was in-creased to 100% B. It was maintained at 100% B for an additional10 min to clean up the column. Dual wavelengths (270 nm and325 nm) were used to detect the eluent composition. HPLC analysis

two cultivars (Blackbell and Millionaire) grown under two different environmentalout with each sample.

Mean(mg/g DMB)(n = 24)

Standard deviation(n = 24)

%RSD(n = 24)

4.11 1.97 48.09

2.63 1.05 40.05

5.94 1.36 22.87

6.71 1.81 27.03

Table 2Total phenolics quantification by Folin–Ciocalteu assay of 32 eggplants extracts belonging to two cultivars (Blackbell and Millionaire) grown under two different environmentalconditions (organic and conventional). Triplicate extraction were carried out with each sample.

Varieties Growing conditions Total phenolicsFolin–Ciocalteu assay GAE (mg/g)Mean (DMB) (n = 3)

Mean(mg/g) (DMB)(n = 24)

Standard deviation(n = 24)

%RSD(n = 24)

Blackbell Conventional 7.08 9.88 2.65 26.81Blackbell Conventional 6.98Blackbell Conventional 9.45Blackbell Conventional 14.99Blackbell Conventional 8.86Blackbell Conventional 11.98Blackbell Conventional 9.11Blackbell Conventional 10.60

Blackbell Organic 6.90 8.90 1.35 15.13Blackbell Organic 7.35Blackbell Organic 9.81Blackbell Organic 9.85Blackbell Organic 10.45Blackbell Organic 7.77Blackbell Organic 9.74Blackbell Organic 9.32

Millionaire Conventional 13.08 11.61 1.26 10.81Millionaire Conventional 13.24Millionaire Conventional 11.61Millionaire Conventional 12.02Millionaire Conventional 9.38Millionaire Conventional 11.04Millionaire Conventional 11.76Millionaire Conventional 10.75

Millionaire Organic 12.24 13.64 2.02 14.78Millionaire Organic 16.62Millionaire Organic 15.85Millionaire Organic 14.62Millionaire Organic 11.73Millionaire Organic 11.22Millionaire Organic 12.36Millionaire Organic 14.47

D. Luthria et al. / Food Chemistry 121 (2010) 406–411 409

at 325 nm was used for quantification of the peak areas of individ-ual phenolic acids.

2.7. Calibration curve

5-Caffeoylquinic acid was quantified with external standards byusing HPLC analysis as described previously (Luthria & Mukhopad-hyay, 2006). Six different standard stock solutions with varying phe-

Table 3Means comparisons in two-way cutlivar � condition ANOVA of eggplant total phenolics (Millionaire varieties) extracts.

Cultivar Condition

Comparison of condition means for each cultivarBlackbell ConventionalBlackbell Organic

Millionaire OrganicMillionaire Conventional

Comparison of condition means for each cutlivarBlackbell ConventionalBlackbell Organic

Millionaire OrganicMillionaire Conventional

Comparison of cutlivar means (conventional and organic combined)MillionaireBlackbell

Comparison of cutlivar means (conventional and organic combined)MillionaireBlackbell

* For each of the 6 pairs of means being compared, different letters indicate statistical d

nolic acid concentration were prepared for 5-caffeoylquinic acid.The concentration of phenolic acids extracted from eggplant sam-ples were calculated using the developed calibration curve equation.

2.8. Statistical analysis

A 2 � 2 (variety � condition) factorial ANOVA was conducted onthe 8 replicate data values observed for phenolics assayed by two

Folin–Ciocalteu) and HPLC (5-caffeoylqunic acid) data of 96 eggplant (Blackbell and

Mean Standard error LSD Group*

Y = 5-caffeoylqunic acid by HPLC4.106 0.563 A2.630 0.563 A

6.709 0.563 A5.943 0.563 A

Y = Total phenolics by Folin–Ciocalteu9.880 0.832 A8.899 0.460 A

13.640 0.832 A11.610 0.460 B

Y = 5-caffeoylqunic acid by HPLC6.633 0.398 A3.368 0.398 B

Y = Total phenolics by Folin–Ciocalteu12.625 0.475 A9.390 0.475 B

ifference between the 2 means at a = 0.05.

y = 1.0864x + 5.7415R2 = 0.8738

10

12

14

16

18

Ass

ay (m

g/g

GA

E)

410 D. Luthria et al. / Food Chemistry 121 (2010) 406–411

independent procedures (Folin–Ciocalteu vs. HPLC analyses). Culti-vars were Millionaire and Blackbell and conditions were ‘conven-tional’ and ‘organic’. Homogeneity of within-(cultivar � condition)variances was tested using a likelihood ratio test by ‘variance-grouping’ factor in the ‘group’ option of the REPEATED statementin SAS Proc MIXED, to indicate which of the 4 cultivars � conditionsexhibited similar variance (SAS Institute Inc., Cary, NC).

0

2

4

6

8

0 2 4 6 8 10 12

5-Caffeoylqunic Acid Content (mg/g)

Folin

-Cio

calte

u

Fig. 2. Correlation between total phenolic content as assayed by Folin–Ciocalteuassay and 5-caffeoylqunic acid, a major phenolic acid in eggplant extract as assay byHPLC using photo-diode array detection.

3. Results and discussion

Identification of phenolics by HPLC and LC–MS analysis hasbeen described in our earlier manuscript (Singh et al., 2009).Fig. 1 shows a typical HPLC chromatogram of the eggplant pulp ex-tract. The most abundant phenolic acid (peak 3) was identified as5-caffeoylquinic acid by comparison of ultraviolet-visible and massspectral data. Peaks 2, 4, and 5 were identified as 4-caffeoylqunicacid, 3-caffeoylqunic acid, and 5-cis-caffeoylqunic acid, respec-tively. Peaks 1 and 6 were not identified.

Accurate quantification of 5-caffeoylquinic acid was carried outusing a purified commercial standard. The results of the HPLC anal-ysis and quantification of 5-caffeoylquinic acid in 32 eggplantssamples is presented in Table 1. The grand mean of 5-caffeoylqui-nic acid content in conventionally and organically grown Blackbellcultivar (24 samples analyzed per growing condition per culti-var = 8 eggplants collected from different plants grown in differentlocations, each analyzed in triplicate) was 4.11 mg and 2.63 mg/100 g of dried eggplant samples. Significant variation in the 5-caf-feoylquinic acid content (2.24–8.30 mg/100 g, % RSD = 48.1%) wasobserved in different eggplant samples collected from differentplants grown under conventional conditions. Similar variations(1.36–4.04 mg/100 g, % RSD = 40.1%) in 5-caffeoylquinic acid con-tent were observed when eggplant samples (cv. Blackbell) weregrown in organic environment. The grand mean 5-caffeoylquinicacid content in conventionally grown eggplant samples (4.11 mg/100 g) was higher than the same cultivar of eggplant sample grownunder organic conditions (2.63 mg/100 g). Relatively, high stan-dard deviation in plant phenolics may be attributed to biologicalvariations between plant-to-plant and their response to environ-mental factors, such as light intensity, stress, and nutrient avail-ability. (Broeckling et al., 2005; Herms & Mattson, 1992).

Assay of TP content in eggplant extracts as quantified by color-imetric Folin–Ciocalteu test also showed similar trend as comparedto the quantification of 5-caffeoylquinic acid by HPLC analysis. Thegrand mean of TP content in conventionally and organically grownBlackbell cultivar were 9.88 mg GAE/g and 8.90 mg GAE/g, respec-tively (Table 2). Thus, conventional grown eggplant contained mar-ginally higher TP as compared to organically grown eggplantsamples. However, analysis of variance showed no statistical dif-ferences in 5-caffeoylquinic acid content in eggplant samplesgrown under organic and conventional environments (Table 3).

Similar to cv. Blackbell, wide variations in the 5-caffeoylquinicacid content (% RSD > 22%) were observed when cv. Millionaireeggplants samples collected from different plants were assayedfor phenolic content by HPLC. The grand mean of 5-caffeoylquinicacid content in conventionally and organically grown cv. Million-aire was reversed with organic grown eggplants showing margin-ally higher grand mean (6.71 mg/100 g) as compared to theconventional grown cv. Millionaire (5.94 mg/100 g). The percentrelative standard deviation of 5-caffeoylquinic acid content in cv.Millionaire grown under conventional and organic environmentswas also lower (�% RSD 25%) as compared to cv. Blackbell (�%RSD 45%). Like cv. Blackbell, analysis of variance showed no statis-tical difference in 5-caffeoylquinic acid content between eggplantsamples grown under organic and conventional environments (Ta-ble 3).

The TP content as quantified by Folin–Ciocalteu assay proce-dures in both Millionaire and Blackbell cultivars also showed sim-ilar trend as compared to the 5-caffeoylquinic acid content assayedby HPLC. Marginally high total phenolic content was measured incv. Blackbell grown under conventionally condition (grandmean = 9.88 mg/g GAE) as compared to Blackbell grown under or-ganic environment (grand mean = 8.90 mg/g GAE). The trend wasreversed with cv. Millionaire where organically grown sampleshad marginally high TP content (grand mean = 13.64 mg/g GAE)as compared to conventionally grown eggplant samples (grandmean = 11.61 mg/g GAE). Analysis of variance showed significantdifference (a = 0.05) in the TP content of organically and conven-tionally grown eggplant samples. The correlation between the TPFolin–Ciocalteu assay and HPLC analysis for all 32 eggplant samplewas strong (R2 = 0.87, Fig. 2). These results suggest that 5-caffeoyl-quinic acid is the major antioxidant phytochemical in eggplants.Statistical analysis of both HPLC and colorimetric Foiln–Ciocalteudata showed significant differences in the phenolic content intwo cultivars (Blackbell and Millionaire, Table 3). Cv. Millionaireshowed higher phenolic content as assayed by two independentprocedures as compared to cv. Blackbell.

These results presented above suggest that it is essential to ana-lyze multiple samples per variety per growing condition in order toquantify phenolic content of different plants and their products assignificant plant-to-plant variation in phenolic content was ob-served. Multiple analyses become critical if one needs to drawany specific conclusions about influence of environment and grow-ing condition on phenolic content. In addition, repetition over mul-tiple growing seasons at different locations should always becarried to unambiguously prove the impact of growing conditionson phenolic content.

4. Conclusions

The HPLC analysis results showed significant plant-to-plantvariations in 5-caffeoylquinic acid content (% RSD ranged from22% to 48%) in eight eggplant samples collected from eight differ-ent plants belonging to same cultivar and grown under similarenvironmental conditions. The cv. Millionaire showed higher phe-nolic content as compared to the cv. Blackbell by both HPLC andFoiln–Ciocalteu assay procedures. No significant consistent trendin the phenolic acid content of eggplant samples was observedwith both eggplant cultivars grown with either organic or conven-tional farming practices. The correlation between total phenoliccontent as assayed by Folin–Ciocalteu assay and 5-caffeoylqunic

D. Luthria et al. / Food Chemistry 121 (2010) 406–411 411

acid, a major phenolic acid in eggplant extract was strong(R2 = 0.87). These results suggest that it is essential to analyze mul-tiple samples per variety per growing condition in order to drawany specific conclusions about influence of environment and/orgrowing conditions on phenolic content changes. In addition, sam-ples grown over multiple seasons at different locations should al-ways be included to unambiguously prove the impact ofenvironment and/or growing conditions on phenolic contentchanges.

Acknowledgements

The authors would like to thank Ms. Allison Setia and Mr. An-drew Anderson for their help in carrying out experimentationand preparation of this manuscript.

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